Variable link aggregation

ABSTRACT

A system and method to transmit frames from a first node to a second node over a plurality of radio links comprising a classifier to classify said frames according to one of a plurality of flow and a sequence number within said one of said plurality of flow and adding said flow and sequence number in a header of said classified frame a splitter receiving said classified frames from said classifier and distributing said classified frames on one of said plurality of radio links for transmission to said second node, a joiner receiving said classified frames and reordering them using an indexed sequence queue corresponding to each of said plurality of flows, a timer for waiting for frames missing in the sequence in one of said indexed sequence queue, wherein when said timer expires, if said frame has not arrived it is deemed lost and a forwarder to extract frames from said sequence queue to forward.

FIELD OF INVENTION

The present disclosure relates to a variable link aggregation, more specifically but not by way of limitation, a system and method for splitting traffic across multiple network links to increase overall throughput.

BACKGROUND

Link aggregation is a widely used, even standardized (e.g., IEEE 802.3ad) technique that splits traffic across multiple network links to increase overall throughput.

Wireless radio equipment is used to construct layer 2 (L2) Ethernet networks in harsh environments where there is little or no existing infrastructure (e.g., oil fields, mines). One property of an unmanaged L2 network is that frames from a source endpoint to its destination endpoint are always delivered in the same order as they are received. In L2 networks that support Quality of Service (QoS), Ethernet frames are classified at ingress and assigned a flow identifier. Frames with a particular flow identifier are delivered in order, but traffic in one flow may be reordered with respect to traffic in other flows. For example, traffic might be classified into high and low priority flows. All high priority traffic is sent in order, and all low priority traffic is sent in order, but high priority traffic is always be prioritized over low priority traffic. Reordering frames between flows is considered acceptable.

A side-effect of transmitting flows in order, is that a single flow is not split across multiple links. This limits the maximum throughput of a single flow to that of a single link. This can be mitigated somewhat by considering more header fields from L3 (or even L4) in the classifier, but the mapping from single flow to single link limitation remains. When backhauling, LTE core traffic is wrapped in the GPRS Tunneling Protocol (GTP) which makes traffic appear as a single flow. As a result, standard link aggregation algorithms do not work for LTE backhaul traffic.

BRIEF SUMMARY

It is the object of the present invention to provide a variable link aggregation. A system to transmit frames from a first node to a second node over a plurality of radio links comprising a classifier to classify the frames according to one of a plurality of flow and a sequence number within the one of the plurality of flow and adding the flow and sequence number in a header of the classified frame. A splitter receiving the classified frames from the classifier and distributing the classified frames on one of the plurality of radio links for transmission to the second node. A joiner receiving the classified frames and reordering them using an indexed sequence queue corresponding to each of the plurality of flows. A timer for waiting for frames missing in the sequence in one of the indexed sequence queue, wherein when the timer expires, if the frame has not arrived it is deemed lost and a forwarder to extract frames from the sequence queue to forward.

In accordance with an aspect of the invention, there is provided a method to transmit frames from a first node to a second node over a plurality of radio links comprising classifying the frames according to one of a plurality of flow and a sequence number within the one of the plurality of flow and adding the flow and sequence number in a header of the classified frame. Receiving the classified frames from the classifier and distributing the classified frames on one of the plurality of radio links for transmission to the second node. Receiving the classified frames, at the second node, and reordering them using one of a plurality of indexed sequence queue corresponding to each of the plurality of flows. Waiting, using a timer, for frames missing in the sequence in one of the indexed sequence queue, wherein when the timer expires, if the frame has not arrived it is deemed lost and extracting the frames from the sequence queue to transmit on a radio link.

In accordance with an embodiment of the invention, the joiner adds a flow identifier to a flow queue upon reception of the classified frames and the forwarder extracts the flow identifier from the flow queue to select which sequence queue to extract the next frame.

BRIEF DESCRIPTION OF THE DRAWINGS

To easily identify the discussion of any particular element or act, the most significant digit or digits in a reference number refer to the figure number in which that element is first introduced.

FIG. 1 illustrates a wireless network with variable link aggregation.

FIG. 2 illustrates an example of frames being classified

FIG. 3 illustrates an embodiment where frames are split onto multiple links.

FIG. 4 illustrates an embodiment where frames are combined from the multiple links.

FIG. 5 illustrates an example of the frame reordering embodiment.

FIG. 6 illustrates another example of the frame reordering embodiment.

DETAILED DESCRIPTION

The details of one or more embodiments of the subject matter of this specification are set forth in the accompanying drawings and the description below. Other features, aspects, and advantages of the subject matter will become apparent from the description, the drawings, and the claims.

Like reference numbers and designations in the various drawings indicate like elements.

FIG. 1 depicts an example embodiment. A first network node 10 receive frames from a network 30. The network 30 may be wired or wireless or a combination thereof. The frames are classified 106 then split across multiple radio transmitters 206 a, 206 b, 206 c for transmission to another node 20. The frames are received at radio receivers 310 a, 310 b, 310 c. They are then joined and sequenced 312 before being forwarded 318 to a network 40.

In one embodiment, the traffic from a single flow is split across multiple links. This introduces the possibility that individual frames in the single flow arrive out of order at the remote node 20. This embodiment optimally splits traffic from a single flow (or multiple flows) across multiple variable speed wireless links and recombines it efficiently at the remote side so proper flow ordering is maintained while still providing predictable Quality of Service (QoS).

FIG. 2 depicts an example of how the frames are classified in preparation for splitting on several links. Frames 102 ready to be transmitted on a radio link arrive at a classifier 106. The size of the box 102 exemplifies a relative size of the frames 102. The number in the box is the arrival sequence number 104 of the frame. The classifier processes the headers to determine the flow identifier of each frame (F) a sequence identifier (S) is also added to each frame 102. In this example, there are four flows 108 a, 108 b, 108 c, 108 d. And each flow has one or more frames arriving in a sequence. In this example, frame #1, #3 and #8 belong to flow A (108 a) The flow identifier (F) a sequence identifier (S) is added to each header 110. In this example, “A/1” indicates the first frame of flow A, “A/2” the second frame in flow A.

FIG. 3 depicts classified frames arriving at a splitter 202. The splitter 202 checks the load factor 204 a, 204 b, 204 c of each radio channel that would result if the current frame was sent to that channel. Then picks the least loaded channel to forward the frame. Calculating the load factor by including the current frame is optional but can improve latency because smaller frames can be sent on radio links 210 a, 210 b, 210 c with fastest transmission bit rate (all else being equal). The link monitor 206 a, 206 b, 206 c monitors the radio 210 a, 210 b, 210 c and update the load meter 204 a, 204 b, 204 c parameters dynamically. If the link goes down, the transmit bit rates goes to zero and the load factor is set to infinity.

FIG. 4 depicts the receive and reassembly side implemented on the receiving radio 310 a, 310 b, 310 c. A joiner function 312 reads frames from radios on a first come first serve basis. It extracts the flow identifier (F) a sequence identifier (S) from each header, then directs the frames to the appropriate sequence queue 316 a, 316 b, 316 c, 316 d based on the flow identifier (F) and slots into each queue based on the sequence identifier (S). A sequence queue is a slotted queue that holds frames indexed by sequence identifier (S). The queues handle out of order and dropped frames using timers.

In a preferred embodiment, the flow identifier is optionally placed in a Flow Queue 314. A forwarder 318 reads the flow identifier at the top of the flow queue 314 and uses it to access the appropriate sequence queue to read from. If there is no frame at the head (dropped or out of order) then the flow identifier is requeued in the flow queue and a timer is started for this flow queue. If a frame is available at the head of the sequence queue, the forwarder reads the frame and forwards it, and if the timer was previously started, it is reset. If there is no frame at the head and the timer has expired, then the forwarder assumes this frame is lost and advances to the next frame in the queue.

The frames exit the forwarder 320 in the right order with respect to their specific flow but can be reordered with respect to other flows and the original frame arrival 322 which does not create an issue.

FIG. 5 illustrates an example of the frame arrival in sequence queue A and the process to reorder the frames. In this example the frame for flow A 316 a with the first sequence number arrives first 510 and the joiner places the frame in the sequence queue and puts A into the flow queue 314. Then the frame with the 3rd sequence number arrives next 512, before the 2nd. The joiner places the third frame in its location in the sequence queue and puts another A in the flow queue 314. The space for the second frame remains empty 514. When the forwarder reads A from the flow queue 314, it reads the first frame 510 and transmits it. The next time the forwarder reads A in the flow queue 314, it sees an empty (“NULL”) 514 entry in the sequence queue 316 b, a timer 520 is started and the forwarder reinserts A back into the flow queue 314. When the forwarder reads A again from the flow queue 314, if the timer expired, packet #2 of the flow A is deemed lost and the forwarder reads and transmits the next packet 512.

FIG. 6 illustrates another example of the frame arrival a sequence queue 316 a and the process to reorder the frames. In this example the frame for flow A with the first sequence number arrives first 510 and the joiner places the frame in the sequence queue and puts A in the flow queue 314. Then the frame with the 3rd sequence number arrives next 512, before the 2nd. The third frame is place in its location in the sequence queue and the joiner puts another A in the flow queue 314 and the space for the second frame remains empty 514.

When the forwarder reads A from the flow queue 314, it reads the first frame 510 and transmits it. The next time the forwarder reads A from the flow queue 314, it sees an empty slot (“NULL”) 514 entry in the sequence queue 316 b, a timer 520 is started and the forwarder reinserts A back into the flow queue 314. When the forwarder reads A again from the flow queue 314, packet #2 518 has arrived and the forwarder reads and transmits it, then resets the timer.

There are a limited number of sequence numbers and the system can use a modulo function to wrap around the number. For example, using 8 bits, there can be 256 sequence numbers (0-255).

The foregoing descriptions of specific embodiments of the present invention have been presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the invention and method of use to the precise forms disclosed. Obviously, many modifications and variations are possible in light of the above teaching. The embodiments described were chosen and described in order to best explain the principles of the invention and its practical application, and to thereby enable others skilled in the art to best utilize the invention and various embodiments with various modifications as are suited to the particular use contemplated. It is understood that various omissions or substitutions of equivalents are contemplated as circumstance may suggest or render expedient but is intended to cover the application or implementation without departing from the spirit or scope of the claims of the present invention. 

What is claimed is:
 1. A system to transmit frames from a first node to a second node over a plurality of radio links comprising: a classifier to classify said frames according to one of a plurality of flow and a sequence number within said one of said plurality of flow and adding said flow and sequence number in a header of said classified frame; a splitter receiving said classified frames from said classifier and distributing said classified frames on one of said plurality of radio links for transmission to said second node; a joiner receiving said classified frames and reordering them using an indexed sequence queue corresponding to each of said plurality of flows; a timer for waiting for frames missing in the sequence in one of said indexed sequence queue, wherein when said timer expires, if said frame has not arrived it is deemed lost; and a forwarder to extract frames from said sequence queue to forward.
 2. The system of claim 1 wherein said joiner adds a flow identifier to a flow queue upon reception of said classified frames and said forwarder extracts said flow identifier from said flow queue to select which sequence queue to extract the next frame.
 3. A method to transmit frames from a first node to a second node over a plurality of radio links comprising: classifying said frames according to one of a plurality of flow and a sequence number within said one of said plurality of flow and adding said flow and sequence number in a header of said classified frame; receiving said classified frames from said classifier and distributing said classified frames on one of said plurality of radio links for transmission to said second node; receiving said classified frames, at said second node, and reordering them using one of a plurality of indexed sequence queue corresponding to each of said plurality of flows; waiting, using a timer, for frames missing in the sequence in one of said indexed sequence queue, wherein when said timer expires, if said frame has not arrived it is deemed lost; and extracting said frames from said sequence queue to transmit on a radio link. 